Dielectric functions and critical points of PbTiO_3, PbZrO_3, and PbZr_(0.57)Ti_(0.43)O_3 grown on SrTiO_3 substrate

摘要

Single crystalline PbTiO_3, PbZrO_3, and PbZr_(0.57)Ti_(0.43)O_3 thin films on SrTiO_3 (001) substrates were grown by a combination of molecular beam epitaxy and rf sputtering methods. The authors measured the dielectric functions of the thin films using spectroscopic ellipsometry and determined the interband critical point energies using standard critical point model. They compared the critical point energies to the band structure calculations in the literature. The data suggest that anticrossing behavior occurs between E_a and E_b near Zr=0.17. This phenomenon is attributed to a coupling between X_(1c) and X_(3c) bands caused by intrinsic alloy disorder.